This application claims the priority of PCT International No. PCT/JP99/04346, filed Japan on Aug. 11, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a turbine-unit disassembling method and a turbine unit. More particularly, the present invention relates to a turbine unit disassembling method and a turbine unit suitably applicable to boiling-water-reactor power plants.
The turbine building of a boiling-water-reactor power plant houses a turbine unit, a generator to be driven by the turbine unit, and so on. The turbine unit comprises a high-pressure turbine and three low-pressure turbines. The turbine unit has to be overhauled periodically.
Each low-pressure turbine comprises a rotor with blades, diaphragms, an upper inner casing and a lower casing to enclose the rotor and the diaphragms, and an upper outer casing to cover the upper inner casing. The casings are so constructed that the upper outer and inner casings can be separated from the lower casing. The upper outer and inner casings are joined to the common lower casing to be ready for the operation of said low-pressure turbine.
To inspect lower-pressure turbines, they are disassembled. Disclosed in the Japanese Unexamined Patent Application No. 11-84049 is a technique for temporarily placing and keeping the disassembled components of low-pressure turbines until they are reassembled.
More specifically, a middle floor is provided along a plurality of low-pressure turbines in such a way that it does not interfere with radiation shielding bodies which protrude upward from the operating floor of the turbine building of a nuclear power plant. The middle floor is supported by supports constructed on the operating floor. The diaphragms disassembled from the low-pressure turbines in such a way are temporarily placed on the racks on the middle floor, and disassembled small components are carried to below the middle floor and temporarily placed there.
Japanese Unexamined Patent Application No. 7-279616 includes a casing for low-pressure turbines with, the casing having a horizontal part on its top portion. Piping is made on the top portion of the casing, and the horizontal part serves as a foothold during the inspection of the piping.
The object of the present invention is to increase the operating ratios of plants with turbine unites.
The first aspect of the present invention is to provide a method of disassembling a turbine unit. The method include the steps of (i) removing the upper outer casings from a turbine unit and placing them at places other than the place of the turbine unit and (ii) removing the upper inner casings from the turbine unit and placing them on the upper outer casings. In accordance with this method, the upper inner casings removed from a turbine unit require no floor space for their temporary placing and keeping because they are placed and kept on the upper outer casings until they are reassembled to the turbine unit. Accordingly, a large working space can be secured, which makes the inspection of the turbine unit easy and quick and, thereby, shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including the turbine unit.
The second aspect of the present invention provides another method of disassembling a turbine unit. The method includes the steps of (i) removing the upper outer casings from a turbine unit and placing them at places other than the place of the turbine unit, (ii) setting a stand over each of the upper outer casings so that the stand straddles said casing, and (iii) removing the upper inner casings from the turbine unit and placing them on the stands. In accordance with this method, the upper inner casings removed from a turbine unit require no floor space for their temporary placement and retention because they are placed and kept on stands, each straddling an upper outer casing, until they are reassemble to the turbine unit. Accordingly, a large working space can be secured, which makes the inspection of the turbine unit easy and quick and, thereby, shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including the turbine unit. Additionally, it is not necessary to consider the strength of the upper outer casings in order to have them support the upper inner casings.
The third aspect of the present invention further provides that each stand has a means for moving horizontally so as to take a position to straddle one of the upper outer casings. This method as well as the method of the second aspect shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including the turbine unit. Furthermore, as with the second aspect, it is not necessary to consider the strength of the upper outer casings in order to have them support the upper inner casings. Moreover, each stand can be set over an upper outer casing without using an overhead crane.
The fourth aspect of the present invention provides yet another method of disassembling a turbine unit. In this method, the upper inner casing of one turbine being disassembled, among a plurality of turbines, is placed on the upper outer casing of another turbine not being disassembled. In accordance with this method, because the upper inner casing of one turbine being disassembled is placed on the upper outer casing of another turbine not being disassembled, the upper inner casing requires no floor space. Accordingly, a large working space can be secured, which makes the inspection of the turbine unit easy and quick and, thereby, shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including the turbine unit. Additionally because the upper inner casing removed from the turbine being disassembled is placed on the upper outer casing of the turbine not being disassembled which is located near the former turbine, the turbine can be disassembled and reassembled in a relatively short time.
The fifth aspect of the present invention provides still another method of disassembling a turbine unit. The method includes the steps of (i) setting a stand over the upper outer casing of one turbine not being disassembled, among a plurality of turbines, so as to have the stand straddle the casing and (ii) placing the upper inner casing of another turbine being disassembled on the stand. In accordance with this method, because the upper inner casing of one turbine being disassembled is placed on the stand straddling the upper outer casing of another turbine not being disassembled, the upper inner casing requires no floor space. Accordingly, a large working space can be secured, which makes the inspection of the turbine unit easy and quick and, thereby, shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including the turbine unit. Once again because the upper inner casing removed from the turbine being disassembled can be placed nearby, that is, above the upper outer casing of the other turbine not being disassembled without imposing a load on the latter turbine, the disassembly and reassembly of the former turbine can be carried out quickly without concern about any other turbine.
The sixth aspect of the present invention provides a further method of disassembling a turbine unit. In this method, the upper inner casings of one turbine unit being disassembled, among a plurality of turbine units, are placed on upper outer casings of other turbine units not being disassembled. In accordance with this method, because two turbine units or more offer temporary-placing places for the upper inner casings of one turbine unit being disassembled, a large space can be secured around it for inspection work. Accordingly, its inspection can be carried out quickly, which shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including such turbine units.
The seventh aspect of the present invention provides the method according to the first, fourth, or sixth aspect, wherein said upper inner casings or casing is placed on supports which are provided on said upper outer casings or casing. This method as well as the methods of the first, fourth, and sixth aspects increases the operating ratio of the whole plant including the turbine unit. Furthermore, upper inner casings or casing can be placed on and supported by the supports stably.
The eighth aspect of the present invention provides a method of disassembling and inspecting a turbine unit. The method include the steps of (i) removing the upper outer casings from a turbine unit and placing them at places other than the place of the turbine unit, (ii) removing the upper inner casings from the turbine unit and placing them on the upper outer casings, (iii) inspecting the turbine unit, (iv) assembling the upper inner casings to the turbine unit, and (v) assembling the upper outer casings to the turbine unit. In accordance with this method, the upper inner casings of a turbine unit can be placed on its upper outer casings just by placing them in the order of their removal, and the outer and inner casings can be left in the one-upon-the-other state until the turbine unit is reassemble. Therefore, a large working space can be secured around the turbine unit for inspection, which can be carried out quickly. Just by lifting the casings, they can be conveyed to the turbine unit quickly in the order of their reassembly. Preferably, the upper outer and inner casings are conveyed with an overhead crane during the disassembly and reassembly of the turbine unit. In that case, it is not necessary to shift the overhead crane from the upper outer casing to the upper inner casing and again to the upper outer casing while they are conveyed. Thus, by using an overhead crane, the turbine unit can be disassembled, inspected, and reassembled quickly.
The ninth aspect of the present invention provides another method of disassembling and inspecting a turbine unit. The method includes the steps of (i) removing the upper outer casings from a turbine unit and placing them at places other than the place of the turbine unit, (ii) setting a stand over each of the upper outer casings so as to have the stand straddle said casing, (iii) removing the upper inner casings from the turbine unit and placing them on the stands, (iv) inspecting the turbine unit, (v) assembling the upper inner casings to the turbine unit, (vi) removing the stands from over the upper outer casings, and (vii) assembling the upper outer casings to the turbine unit. In accordance with this method, the upper inner casings of a turbine unit can be placed above its upper outer casings just by placing them in the order of their removal, in the same way as the method of the eighth aspect except for the use of stands. includes the steps of (i) removing the upper outer casing from one turbine being disassembled, among a plurality of turbines, and placing it at a place other than the place of the turbine, (ii) removing the upper inner casing from the turbine and placing it on the upper outer casing of another turbine not being disassembled, (iii) inspecting the disassembled turbine, and (iv) assembling the upper inner casing to the disassembled turbine. In accordance with this method, the upper inner casing of one turbine being disassembled is placed on the upper outer casing of another turbine not being disassembled. Therefore, the floor space otherwise occupied by the upper inner casing can be used for the inspection work of the components of the disassembled turbine. Accordingly, a large floor space for inspection can be secured, and the inspection can be carried out quickly. Furthermore because the turbines of a turbine unit are arranged adjacent to each other, the conveying distance of the upper inner casing of a turbine being disassembled is short and, hence, the conveying time of the casing is short. Therefore, the turbine unit can be disassembled, inspected, and reassembled quickly.
The eleventh aspect of the present invention provides still another method of disassembling and inspecting a turbine unit. The method includes the steps of (i) removing the upper outer casing from one turbine being disassembled, among a plurality of turbines, and placing it at a place other than the place of the turbine, (ii) removing the upper inner casing from the turbine and placing it on a stand which is set in advance over the upper outer casing of another turbine not being disassembled so that the stand straddles the casing, (iii) inspecting the disassembled turbine, (iv) assembling the upper inner casing to the disassembled turbine, and (v) assembling the upper outer casing to the disassembled turbine. In accordance with this method, the upper inner casing of one turbine being disassembled can be placed above the upper outer casing of another turbine not being disassembled in the same way as the method of the tenth aspect except for the use of a stand. Therefore, the turbine unit can be disassembled, inspected, and reassembled quickly.
The twelfth aspect of the present invention provides a turbine unit wherein each turbine comprises (i) a rotor with blades, (ii) an upper inner casing and a lower casing for enclosing the rotor, and (iii) an upper outer casing for covering the upper inner casing, the upper outer casing having supports which are so positioned as to receive and support the bottom surface of the upper inner casing outside the upper outer casing. Because the upper inner casings removed from the turbine unit can be placed on the upper outer casings removed from the same, the former casings require no floor space. Therefore, a large space can be secured for the inspection of the turbine unit. Accordingly, the inspection can be carried out quickly, which shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including the turbine unit.
The thirteenth aspect of the present invention provides a turbine unit wherein each turbine includes (i) a rotor with blades, (ii) an upper inner casing and a lower casing for enclosing the rotor, and (iii) an upper outer casing for covering the upper inner casing, the upper outer casing having reinforcing ribs on its outer surface and supports which are provided on the ribs in such positions as to receive and support the bottom surface of the upper inner casing. As in the case of the turbine unit of the twelfth aspect, the upper inner casings removed from this turbine unit can be placed on the supports of the upper outer casings removed from the same. Therefore, a large space can be secured for the inspection of the turbine unit. Accordingly, the inspection can be carried out quickly, which shortens the nonoperating time of the turbine unit and increases the operating ratio of the whole plant including the turbine unit. Furthermore, the supports are provided on the reinforcing ribs of the upper outer casings, the strain of the upper outer casings is prevented and they can support the upper inner casings firmly.
The fourteenth aspect of the present invention provides the turbine unit according to the twelfth or thirteenth aspect, wherein each of said supports has a stopper protruding upward from its top surface. This turbine unit as well as the turbine units of the seventh and the eighth aspects increases the operating ratios of power plants. Besides, the stoppers of this turbine unit prevent the upper inner casings from sliding on and falling off the upper outer casings.